Napster has announced it is to start selling music with less restrictions.

Following in the path of other online retailers, Napster has told the press that the it is soon to start selling music downloads as unprotected MP3 files.

The file format change will apply only to single tracks and album purchases, according to a company press release.

Tracks downloaded as part of the company's music subscription service will continue to have copyright restrictions.

Chris Gorog, Napster's chairman and chief executive said in a statement: "The ubiquity and cross-platform compatibility of MP3s should create a more level playing field for music services and hardware providers and result in greater ease of use and broader adoption of digital music".

According to online reports, Napster has not yet revealed which record companies had agreed to license music for sale as MP3s via Napster.

Last year, Vivendi's Universal Music Group, Warner Music Group Corp and EMI Group gave permission for some online retailers, including Amazon, to sell their artists' music as unprotected MP3 files.

Analysts are predicting that Sony BMG Music Entertainment will follow this year.

Napster recently told subscribers that it will increase fees on its basic subscription plan from $9.95 to $12.95 a month from 30 January. It gave existing subscribers the option to lock in the lower monthly fee if they paid for a full year in advance.